1. Field of Art
This invention relates to the improvement of an agricultural combine harvester. More specifically it relates to an improvement of the heating, ventilation and air conditioning system of a combine harvester.
2. Description of Prior Art
Mechanical harvesting of grain has taken place for decades. However, efforts continue in the attempt to make harvesting operations more efficient and effective. A combine harvester generally includes a head which cuts the crop. The head then moves the cut crop into a feeder house. The feeder house lifts the cut crop into the threshing and separation areas of the combine. The grain is separated from the stalk by a rotor or threshing system. The grain is then moved and stored in a grain tank. The chaff and trash are deposited from the rear of the combine. An operator usually runs these various operations from a glass-enclosed cab. Typically, a cab is located behind the head and in front of the threshing and separation areas of the combine. An operator can observe most of the combine activities from the cab. During harvesting periods it is not uncommon for the combine to be operated for an extended time. Sometimes a single operator will use a combine for 16 to 18 hours a day. Furthermore, several operators may alternate in the use of the combine. Therefore is it necessary to provide a cab which will allow maximum operator comfort and flexibility. This will permit the operator to remain mentally alert for the long time intervals needed to harvest crops. Aspects of maintaining the operator's alertness includes providing a combine cab which is environmentally controlled by a heating, ventilation and air conditioning (HVAC) system.
The effort to design and manufacture a better combine cab is considerable and has taken several approaches. In the early days of combine harvesting, there were no cabs and the operator was exposed to the outside elements during farming operations. During combine operations, a considerable amount of particulates are released in the air. Furthermore, the noise created by engine, header and threshing system is quite loud. Current cab design focuses on having a heating, ventilation and air conditioning system to maintain a comfortable working environment inside the cab. Current cab design also focuses on maintaining a good view of the header. Both of these focuses have resulted in several shortcomings. Usually the heating, ventilation and air conditioning unit is positioned either under the driver's chair or in the cab ceiling. When the unit is positioned under the driver's chair, dust or dirt can easily enter the return air system degrading or possibly damaging the unit. Also by positioning the unit beneath the seat, the distribution ducts are inserted in the roof posts. This necessitates the post circumference be increased to allow for air passage. This results in a greater obstruction to viewing the farming operations. When the unit is located in the ceiling of the cab, the condensation can drip into the headliner of the cab or onto the operator or control equipment. Periodically it may be necessary to remove the cab to perform work on the threshing system. Also it is frequently necessary to clean the heater and evaporator cores. This is difficult to accomplish in a roof or floor-mounted system. Also, because the engine coolant and refrigerant lines are moved, the ethylene glycol and the refrigerant contained within those lines is usually vented. Because of environmental concerns this adds considerable expense.
The prior art illustrates these and additional difficulties. U.S. Pat. No. 4,088,364 discloses an environmental control system and cab combination. This design places the air conditioner unit beneath the operator's chair. The return air intake 116 is located in close proximity to the cab floor. The fresh air is forced through the cab posts from an opening near the ceiling. As mentioned previously, dirt and dust on the operator's shoes would be drawn into the return air filter. The size of the cab post needs to be increased to accommodate the fresh air. The larger posts inhibit the operator from viewing the header or grain tank unloading auger (as seen from the rear of the cab). The placement of the air conditioning unit beneath the operator's chair also limits the space within the cab.
U.S. Pat. No. 5,538,472 discloses an agricultural vehicle cab temperature control system. Again, a portion of the cooling system is located beneath the driver's chair. When the cab is removed the heat exchanger lines must be separated and coolant and refrigerant is released. By moving the HVAC unit from the cab, there are several remote controls between the cab and HVAC unit. The cables to between the interior of the cab to the cab exterior creates a `noise conduit` which allows the noise to travel into the cab.
Consequently, the need exists for a cab of a combine harvester such that the operator has an unobstructed view of farming operations, which is spacious, has a well-designed environment system and allows for easy access to the threshing systems.